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Semiconductor Thermometers Classification of Semiconductor Thermometers Semiconductor thermometers (Sachse, 1975) are made from materials which are neither conductors nor insulators. Research of the thermal properties of semiconductors was first reported by William Faraday in 1834. Their industrial production was started at the Bell Telephone Company and, simultaneously, at Osram in 1930. It is apparent from the work of many authors such as Sze (1969) and van der Ziel (1968), among others, that these materials may have an intrinsic, or pure form, a compound form or a doped form. Compound and doped semiconductors are often called extrinsic semiconductors | Temperature Measurement Second Edition L. Michalski K. Eckersdorf J. Kucharski J. McGhee Copyright 2001 John Wiley Sons Ltd ISBNs 0-471-86779-9 Hardback 0-470-84613-5 Electronic 5 Semiconductor Thermometers Classification of Semiconductor Thermometers Semiconductor thermometers Sachse 1975 are made from materials which are neither conductors nor insulators. Research of the thermal properties of semiconductors was first reported by William Faraday in 1834. Their industrial production was started at the Bell Telephone Company and simultaneously at Osram in 1930. It is apparent from the work of many authors such as Sze 1969 and van der Ziel 1968 among others that these materials may have an intrinsic or pure form a compound form or a doped form. Compound and doped semiconductors are often called extrinsic semiconductors. Thermometers of this type which may use bulk material temperature dependencies or junction effect carrier density relations may be classified by the number of electrodes and number of junctions possessed per sensor. This ordering is based upon that used by Sze 1969 in the classification of semiconductor devices. There are two main groups of semiconductor thermometers Bulk effect two-electrode sensors which belong to the resistive group possess no semiconductor junctions. They are thermistors or silicon-RTDs also called Silistors by Hyde 1971 . Junction device sensors are either diodes with one junction and two terminals transistors with two junctions and three terminals or integrated circuit sensors with multiple junctions and numbers of terminals. Semiconductors exhibit strong temperature dependent behaviour. From fundamental physical considerations it can be shown that extrinsic semiconductors possess three main regions of temperature dependence. In doped materials at temperatures below about 150 K and particularly within the cryogenic range there are practically no minority carriers as most material impurities are frozen out . The other two .